Recently, researches using various types of nanoparticles are being actively conducted in biomedical fields such as cell staining, cell separation, drug delivery system, gene transfer, diagnosis and treatment of disease or disorder, and molecular imaging.
For example, drug delivery technology, which is a technology of treating disease by delivering drug to the affected area directly or indirectly without diffusion of the drug in the body, prevents side effects which may be caused by acting of the drug on healthy areas in the body, and can also significantly reduce the drug dosage as compared with general methods. Particularly, an antitumor agent should have not only an effect on cancer cells but also low toxicity and excellent solubility in order to be used for a clinical trial. Many new drugs ended in failure in a clinical trial during the development thereof because they were lacking in one or more of such requirements. Recently, researches on a drug delivery system are intensively being carried out because the drug delivery system can have a possibility of preventing healthy cells from toxicity, or the like. However, through current technology, it is impossible to operate two or more drugs with a time lag, and thus drug delivery with various drugs combined is impossible.
Therefore, to operate two or more drugs at an affected area with a time lag or at different affected parts simultaneously, development of drug delivery system and a bio-applicable magnetic particle which are capable of selectively operating is urgent.